// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CC_LAYERS_LAYER_LIST_ITERATOR_H_
#define CC_LAYERS_LAYER_LIST_ITERATOR_H_

#include <stdlib.h>
#include <vector>

#include "cc/base/cc_export.h"

namespace cc {

class LayerImpl;

// Unlike LayerIterator and friends, these iterators are not intended to permit
// traversing the RSLL. Rather, they visit a collection of LayerImpls in
// stacking order. All recursive walks over the LayerImpl tree should be
// switched to use these classes instead as the concept of a LayerImpl tree is
// deprecated.
template <typename LayerType>
class CC_EXPORT LayerListIterator {
public:
    explicit LayerListIterator(LayerType* root_layer);
    LayerListIterator(const LayerListIterator<LayerType>& other);
    virtual ~LayerListIterator();

    bool operator==(const LayerListIterator<LayerType>& other) const
    {
        return current_layer_ == other.current_layer_;
    }

    bool operator!=(const LayerListIterator<LayerType>& other) const
    {
        return !(*this == other);
    }

    // We will only support prefix increment.
    virtual LayerListIterator& operator++();
    LayerType* operator->() const { return current_layer_; }
    LayerType* operator*() const { return current_layer_; }

protected:
    // The implementation of this iterator is currently tied tightly to the layer
    // tree, but it should be straightforward to reimplement in terms of a list
    // when it's ready.
    LayerType* current_layer_;
    std::vector<size_t> list_indices_;
};

template <typename LayerType>
class CC_EXPORT LayerListReverseIterator : public LayerListIterator<LayerType> {
public:
    explicit LayerListReverseIterator(LayerType* root_layer);
    ~LayerListReverseIterator() override;

    // We will only support prefix increment.
    LayerListIterator<LayerType>& operator++() override;

private:
    void DescendToRightmostInSubtree();
    LayerType* current_layer() { return this->current_layer_; }
    std::vector<size_t>& list_indices() { return this->list_indices_; }
};

} // namespace cc

#endif // CC_LAYERS_LAYER_LIST_ITERATOR_H_
